/Engine/Source/Runtime/Core/Public/Misc/MapErrors.h
Maps need lighting rebuilt: This warning is caused when lighting has been invalidated by moving or modifying a light actor. This can cause problems because the rendered lighting in the level is not accurately representing the current state of lights in the level. This error can be solved by going to the Build menu and rebuilding lighting for a map.
static [FLazyName](API\Runtime\Core\UObject\FLazyName) RebuildLighting;